The Carillon: How it Works
by Adelheid Rech (part two)
by Adelheid Rech (part two)
In order to understand the art of the carillon we must know something about both its complex structure and how it is constructed. For this we shall first have a look at the shape and acoustics of a single bell, and afterwards, the structure and technique of the carillon, including the two principal playing techniques.
Compared to modern standards, the early carillons were primitive constructions. Bells were uneven in quality and the musical effect they were able to produce was greatly inhibited by crude playing actions. Evidence suggests that the technical skills of early founders were far from uniform. However, those engaged in this enterprise were eventually able to earn international reputations as master craftsmen.
The shape of a true bell is derived from two basic forms: the cup and the hollow sphere. The cup form or "open" bell is more common and is used in a great variety of profiles for almost all kinds of Western European tower bells. The sides of this form flare out from the top slightly for two-thirds of their length and then more rapidly towards the bottom.
The hollow sphere form or "closed bell" is of the same ancient origin and appears in as many varieties of shape as the open bell. The bell's sound it produced by a loose pellet enclosed inside. A representative example of the closed bell is the sleighbell (French: grelot, German: Schlittenglocke).
The closed bell is far more complex acoustically than any other vibrating body intended for musical purposes, and its manufacture presents daunting challenges. The shape of a common open bell consists of a head or "vertex," shoulders, waist, the "sound bow," the "lip" or rim as the lower edge and the open "mouth." With the increase in flare at the outside there is also an increase of the thickness of the bell's wall. The maximum thickness occur near the rim where the clapper or hammer strikes the bell, called the sound bow.
The device which serves to attach or suspend the bell is normally a loop or crossed loops ("crown") at the vertex, although in many modern bells it is simply a bolt hole. The sound is produced either by the clapper (usually a rod with a knob) that strikes the sound bow from inside (mainly used by the keyboard for manual playing or by swinging the bell), or with a hammer, striking on the outside (used by the automatic clock chime mechanism). The hammer is usually permanently affixed close to the bell and is activated by remote control. This all means that the carillon bells do not move in performance.
Due to the bell's resonating material, geometric form and characteristic contour, a stroke, whether from inside or outside, causes not only one single tone but a multiplicity of frequencies. The whole results in a homogeneous mass of vibrations which are interrelated and interacting.
The five principal tones of a bell are carefully tuned by the bell founders after the cast process (click here to see Jacob van Eyck and the Hemony brothers). The lowest partial is called the "hum tone" (Fr. bourdon, Ger. Unteroktave). It sounds throughout the bell. An octave above is the "prime" or "fundamental" (Fr. principal, Ger. Prime). This is the most prominent "tone" (or better chord sounding in unity) heard when the bell is struck, therefore called "slagtoon" or "strike" note. Its pitch defines the note of the bell. The next is a "tierce" (Fr., Ger. Terz), a minor third above the fundamental which gives the bell a somewhat mournful sound (and later caused extensive discussions and research).1 It is located above the sound bow. Above the tierce is the "quint" (Fr. quinte, Ger. Quinte) or "fifth," and the last is the "nominal" (Fr. nominal, Ger. Oberoktave) sounding an octave above the fundamental and two octaves above the hum tone.
The profile of a bell is responsible for modes of vibration that determine not only the frequencies of the various partials but their intensities as well. The lower area at the lip is the most important vibrating part of the bell being more flexible and having more mass. During the first moment after a stroke, the three octaves—nominal, fundamental and hum tone—establish the basic pitch, but other partials, tuned or untuned, contribute significantly to its timbre. The partials fade at different rates, with higher frequencies dampening more rapidly than lower ones. The bell's tonal decay undergoes a subtle and continuing transformation which varies according to the size and profile of the individual bell.
Carillons from the seventeenth century, the exquisite Hemony-carillons in particular, could encompass about three chromatic octaves (c. 36 bells). An average modern carillon ranges in size from four or four and one half chromatic octaves (c. 48–56 bells). Some carillons in America have a range of up to six octaves with as many as 77 bells.
The bells are usually hung in a bell chamber in various arrangements depending on space, number and size of the bells, as well as on the height and construction of the tower. When the bass bells are large, they are usually placed below the playing cabin in order to make a better tonal distribution.